It looks a little long to me, too, but I can't tell if it is damage or some other oddity. Click on the link for some images. https://www.bing.com/images/search?q=1987+d+lincoln+cent&qpvt=1987d+lincoln+cent&FORM=IGRE Chris
I think it might be the same slide the D took on strike. It was a hot part of the penny and the copper sheeth shifted. At first I thought someone might have just took a flame to the penny but there's no discoloration or black area on the other side. That dark part goes all the way up to the "we trust".
Could be just a small plating blister under the 7 that gives it the appearance of it looking longer. Plating blisters can appear anywhere on a copper plated zinc Cent.
You know, you're right. While it is long, comparing to the other pennies, it's definitely not as pronounced as when I first saw it. I think maybe I'm gonna have to sit on any errors I come across before posting. I've noticed that after looking at penny after penny for errors, my eyes and mind start to play tricks on me. I've never had to walk a hot desert, but I think falling for a mirage works on the same principle. Only this is a penny mirage. It's nearly impossible to tell someone who's fallen for a mirage that it's not what he thinks. This is all a guess mind you, but it would explain why some people have a hard time seeing reality.
Just remember having a trained eye, takes time and practice. Determining die states, strike and amount of luster takes time, add in circulation and most have a hard time determining what they see. Hang in there, figure the direction you want to go and study it! Good luck @Tin_Man_0
I think your mentality is promising for you learning and finding the good stuff down the road. We all started out in numismatics ignorant of very basic things. I once had a cent I was convinced had gold or brass struck into it. Turns out it was from acid. The best thing you can do is read up on how errors are made and how to identify them. This website has great explanations and illustrations: http://www.error-ref.com/